Improving Augmented Reality: Ion Beam Processing of Slanted Surface Relief Gratings (SRG)

Optical patterns, especially surface relief gratings (SRG), are becoming ever-important, with applications ranging from laser mirrors to mixed and augmented reality (MR/AR) devices. In particular, slanted surface relief gratings are essential as in- and out-couplers of light into the waveguide to produce lightweight near-eye AR displays. They allow to suppress higher diffraction orders, maximize light yield, and achieve a wide field of view. The pattern can either be etched directly into the waveguide by reactive ion beam etching (RIBE) or be produced through nano-imprint lithography (NIL). NIL requires the production of a master stamp with defined grating properties. Reactive ion beam trimming (RIBT) is a suitable technology for producing master stamps as it allows manufacturing gratings with varying trench depths and slant angles over a substrate. In addition, it is shown how the shape of the slanted grating can be improved by applying different process parameters.